Jekyll date fixes and not respecting GUIDs

A brief housekeeping note and apology if I duplicated a bunch of posts in your blog reader. Earlier this week I put an SSD in my Mac Pro and had to reformat OS X; then I promptly forgot to set my TZ environment variable. This reset all the dates on everything, which some readers construed as new posts.

Defining GUIDs was supposed to prevent this behavior.I suppose enough readers have seemed malformed feeds with duplicated GUIDs, and define uniqueness from a mix of attributes.